Air leakage is an essential factor contributing to overall building performance. It plays a major role in determining energy consumption in harsh climates, particularly in residential buildings, as it represents a significant component of the envelope-induced thermal load. In centrally air-conditioned houses, the HVAC system can substantially alter the pressure distribution across the exterior envelope, reforming the air leakage behavior. Nonetheless, limited information is available to characterize and better understand such behavior to accurately predict building performance and energy consumption toward meeting the emerging requirements for sustainable buildings. This study experimentally investigated the air leakage behavior of a selected sample of centrally air-conditioned typical single-family detached houses in Saudi Arabia. The air leakage behavior was investigated by measuring the overall airtightness and the contribution of the different air leakage paths using the viable method of the blower door test (BDT). The air leakage rate was then calculated using the measured induced pressure across the envelope during the HVAC system operation. Results indicated that the air leakage behavior is significantly altered by the pressurization induced by the central HVAC system, eliminating air infiltration and producing an outward airflow across the entire envelope. The study addresses a current challenge in characterizing envelope air leakage behavior for a common type of house and, thus, would indirectly contribute to more accurate thermal and energy performance assessments. Several aspects were highlighted for consideration when defining the contribution of air leakage to energy consumption prediction and studying air leakage behavior in other types of buildings.

External corrosion is one of the major defects for oil and gas pipes. Multiple repair techniques are used for repairing such pipes, which have different environmental effects. In this study, the life cycle assessment (LCA) approach has been used to investigate the environmental impacts of four commonly used repair techniques. The techniques are fillet welded patch (FWP), weld buildup (WB), mechanical clamp (MC), and non-metallic composite overwrap (NCO). The repair processes based on guidelines from repair standards are carried out on a defected pipe specimen and experimental data required for LCA are collected. The paper conducts a cradle-to-gate LCA study using SimaPro software. Six environmental impact categories are used for the comparison of repair processes. The results for a repair life of ten years indicate that non-metallic composite overwrap has the highest whereas the fillet welded patch has the lowest environmental impacts.

Energy-efficient building envelope design is essential for minimizing cooling loads and reducing energy consumption, particularly in hot desert climates. This study presents a model that optimizes insulation thickness by taking into account climate-specific conditions and economic factors. The model employs a life-cycle cost analysis framework, incorporating energy savings, insulation costs, and payback periods across various climatic zones. A typical wall is considered with three commonly applied insulation materials. The optimization is validated by energy modeling. A key contribution of this study is the introduction of a correction factor based on average humidity for each city, which adjusts the conduction-based model to account for latent heat effects from moisture-dependent insulation degradation. Unlike existing building codes, which prescribe fixed insulation requirements regardless of regional climate conditions, our approach dynamically adapts insulation thickness based on Cooling Degree Days (CDDs) and economic feasibility. The results reveal significant variations in optimal insulation thickness across different cities, demonstrating the necessity of climate-responsive insulation strategies. The analysis indicates that locations with higher CDD, such as Jeddah and Dhahran, require thicker insulation to reduce cooling loads effectively, whereas cities with lower cooling demand, such as Khamis Mushait, necessitate thinner insulation for economic viability. The results show that polystyrene (K = 0.034 W/m.K) has the least cost, whereas polyurethane (K = 0.24 W/m.K) records the least thickness in Saudi Arabia. This study presents a model that optimizes insulation thickness by taking into account climate-specific conditions and economic factors.